George, when you say "the £30 version" I guess you are meaning the H&W Hydraglide, not the Cortesi (pretty good) £30 'pin also from Dragon Carp? I just looked on DC website and they don't seem to sell the Hydraglide one now anyway - I don't actually remember seeing it, but I know it got slated.
I assume Holland & Wilkinson is a made up Olde English type sounding name by Dragon Carp, same as the made up "Marco Cortesi" name (read somewhere it was butcher's name they saw on a van or something!). Interesting you rate the Rotoglide highly as I wasn't sure if it was a bit of a gimmick with its fancy box and mock vintage name.
ps - oil - I had trouble getting some sewing machine oil quickly but found that hair clipper oil works well, also the expensive valve oil from my lad's french horn


I suppose its just any very fine high quality oil, rather than your thicker 3 in 1 stuff.